The purpose of this project is to study the reversal of preneoplastic bladder lesions by retinoids (vitamin A and its analogs) in organ culture. Areas of specific interest include (1) the effects of retinoids on in vitro induced hyperplasia and dysplasia; (2) the effects of retinoids on in vivo carcinogen-induced hyperplasia and dysplasia; and (3) the functional relationships between retinoids and glucocorticoids. BIBLIOGRAPHIC REFERENCE: Reese, D.H., Friedman, R.D., Smith, J.M., and Sporn, M.B. Organ culture of normal and carcinogen-treated rat bladder. Cancer Res., 36: 2525-2527, 1976.